Timeline / Requirements for GRASS project

Monday March 12th 2007, Deadline for OSGeo submission as an organization

We must list of potential mentors for GRASS work

March 24: Student application deadline.

April 9: Accepted student applications announced.

May 28: Students begin work.

August 31: final evaluation deadline.

Improved Line of Sight Analysis in GRASS

Line of sight determination is a very important analysis to have available in a GIS. The GRASS module that currently performs this function, r.los, has a number of limitations, including being very slow to run and unable to handle large high-resolution datasets. The task: write a new r.los module based on the paper 'A Fast Algorithm for Approximate Viewshed Computation' published in 'Photogrammetric Engineering & Remote Sensing' July 2003:
http://www.asprs.org/publications/pers/2003journal/july/2003_jul_767-774.pdf
Incorporate features of r.cva (http://www.ucl.ac.uk/~tcrnmar/GIS/r.cva.html), which cannot currently be incorporated in GRASS for licensing reasons, and extend with other functionality as appropriate.

The work will involve familiarisation with the GRASS raster library for reading and writing maps, the GRASS vector library for reading analysis location sites. It is expected that the GRASS directed graph library will also be useful for implementing many features of the algorithm (specifically, determining the crossing points and distances between the cells).

A new simulation/optimization algorithm for least cost path

A new module which would calculate the shortest path from a starting point to a destination. It would use dijkstra's algorithm do find the shortest path in a weighted network. In other words it would treat a cost surface (generated by r.cost) as a network and then calculate the shortest path. This differs from r.drain in that r.drain is a local function, greedy algorithm, whereas this a focal algorithm, that is it takes not only it's immediate location into account, and finds a global shortest path.

This will involve reading and writing raster maps.

Potential Mentor

Wolf Bergenheim

Shortest path in free (vector) space (avoiding obstacles)

This module would take as input a vector map with polygons. These polygons would be treated as obstacles. It would also take a starting and end point as input. It would output a vector map containing the shortest path in free space (this assumes an equal cost surface). There are 2 different ways to do this calculation:

by building a "road network" with the help of building trapezoids from each corner point of the obstacles.

OR PREFERABLY

by building a visibility graph and converting it into a weighted network and running Dijkstra's shortest path on it.

This project will be vector and will also involve the directed graph library when calculating the shortest path.

Further work on r.li

The r.li module recently entered official GRASS code base. It is meant as a faster and more manageable replacement for r.le for the analysis of landscape ecology and composition. To replace it fully, we need:

implementation of other indices

remove the dependency on TclTk, so as to prepare it for the coming python GUI

further testing and bugfixing

Potential Mentor

Paolo Cavallini

Other ideas

better implement PostGIS support (I do not think this is very useful --Cavallini 07:48, 13 March 2007 (CET))